Fan equipment



S. H. DOWNS FAN EQUIPMENT Sept. 8, 1959 Filed Oct. 17, 1957 2Sheets-Sheet 1 Sept. 8, 1959 s. H.l DowNs 2,903,182

FAN EQUIPMENT Filed Oct. 17, 1957 l 2 Sheets-Shee 2 United States PatentOilice Patented Sept. 8, 1959 FAN EQUIPMENT Sewell H. Downs, Kalamazoo,Mich., assignor to Clarage Fan Company, Kalamazoo, Mich., a corporationof Michigan Application Getober 17, 1957, Serial No. 690,726

4 Claims. (Cl. 23o-130) This invention relates in general to amulti-stage blower and, more particularly, to a type thereof having apair of inlet boxes which are disposed between, and communicaterespectively with, a pair of spaced single inlet blower housings, eachof which contains a blower wheel mounted upon the same shaft structure.

A recognized need has long existed for air handling equipment capable ofmoving relatively large volumes of air -at relatively high outletpressures, without sacricing eciency and at a reasonable cost. Presentconventional blower runits are incapable of producing the desiredpressures -without exceeding permissible tip speeds and/ or soundlevels. As a result of this, centrifugal compressors are being used morefrequently, particularly in multiple stages, to provide the higherpressures which are demanded. However, such compressors are presentlymade from carefully machined parts which are relatively costly topurchase originally and, also, are costlyto maintain, particularly inheavy duty operations where replacements are often needed. Furthermore,the volume produced by such compressors is relatively small bycomparison with the cost of the installation.

It has previously been recognized that, if two or more centrifugalblower units could be staged in an efficient manner, it would bepossible to produce substantially larger pressures than are presentlyavailable with a single blower unit, while at the same time maintainingthe lower cost and the higher volumes of centrifugal blowers, bycomparison with compressors. It is also recognized that, if the airmoving from one stage to another has rotational components around theblower wheel axis as it enters the blower unit of the higher stage,there will be a correspending reduction in capacity. In one form ofmultiple blower installation, two or more conventional, otherwiseindependent, blower -units are serially interconnected by the ductsconnecting the outlet of one to the inlet of another. Where, forexample, two blower |units are so arranged, the space requirements areat least double, as compared with a single unit, and the costs are verymaterially increased. Even though the increased cost may be acceptable,the increased space requirements are `frequently unacceptable.

Another type of multiple blower installation comprises a double width,double inlet, blower unit having inlet boxes on the opposite sidesthereof. A divider plate encircles the double width wheel substantiallyco-planar with the center plate thereof, thereby dividing the doubleunit into two single units. However, this arrangement necessitates theuse of a very large and heavy shaft and correspondingly heavy bearingstructures. More specifically, the shaft must be large and strong, bothbecause of its long span and because the blower Wheel is mounted at thecenter of such span. Furthermore, because of the necessarily largediameter of the shaft at its center, the wheel hub must becorrespondingly large and heavy. The oversized hub not only further`aggravates the shaft size problem, but also produces a reduction in theperformance of the blower wheel. Thus, not much is gained by using sucha structure, except for saving some space by eliminating two of the fourbearing assemblies, which would lbe required by simply providing twoseparate units. There is no saving in cost because of the increase incost of the oversized shaft, the oversized hub structure for the blowerwheel and the oversized bearing structures required to support theoversized shaft. Furthermore, the resultant structure is relativelyheavy and dicult to install, particularly where large units arerequired.

Another problem, which is characteristic of the double width assembly,arises when the two sides of the assembly are interconnected. As statedabove, the double width blower housing is divided by a central wallwhich, at least in eiect, produces two single width blower units. Inorder to stage these two units, the outlet Ifrom one blower unit must beconnected by a diuct to the inlet box of the lother unit, whichnecessitates that the connecting duct pass around the other blower unit.Often, particularly in large installations, it is desirable, if notessential, that both blower units discharge in the same direction. Thus,the interconnecting duct must either block the outlet of the blowercrossed over or it is necessary to make this crossover through a verytort-uous path, which not only adds to the cost of the installation, butalso often introduces rotational components in the air flow whichmaterially reduce the capacity of the unit and may even prevent its use.

Accordingly, a primary object of this invention has been the provisionof a multi-stage blower Structure capable of producing -a relativelyhigh total pressure with a minimum of loss in capacity and/oreiliciency, with a minimum of increase in cost of fabrication andoperation, and with an absolute minimum of space required for theinstallation.

A further object of this invention has been the provision of a two-stageblower construction wherein the operational and performance advantagesof single blower units are retained, wherein the space required for theconnections between, as well las with, the two blower units is held toan absolute minimum while the construction remains capable of variationin installation arrangements, and wherein the weight of the blowerwheels is supported upon the shaft substantially adjacent to the shaftsupporting bearings, thereby minimizing the size of the shaft requiredto support the wheels.

Other objects and purposes of this invention will become apparent topersons familiar with this type of equipment upon reading the followingspecioation and examining the accompanying drawings, in which:

Figure 1 is a side elevational View of a two-stage blower assemblycharacterizing the invention.

Figure 2 is atop plan view of said two-stage blower assembly.

Figure 3 is a sectional View taken along the line III-III of Figure 2.

Figure 4 is` a side View of a modied struct-ure.

For the purpose of convenience in description, the terms upperj lowerand derivatives thereof will have reference to the two-stage blowerassembly in its normal position of operation, as shown in Figures l and3. The terms innen outer, and yderivatives thereof will have referenceto the geometric center of the blower assembly and parts thereof.

General description ln order to meet the objects and purposes of thisinvention, including those set forth above, there has been provided atwo-stage blower assembly comprised of a pair of single width, singleinlet, blower housings spaced from blower housings so that theycommunicate with the inlet openings in their respective housings. Ashaft, which extends through said blower housings and said inlet boxescoaxially with. said inlet' openings, ,is supportednear-ts opposite/endsupon-'a 'pair of bearing' assemblies'located onthe remotesidessof'said.blower housings. A pair of single'width,l single inlet, blower wheels'are mounted upon said-shaftwithin -theirrespectivey housings and,therefore, adjacent, respectively, to the bearing assemblies. The outletof one blowerhousing-.and theinlet ofthe inlet box associated with theother'blower housing preferably open in substantially the-same directionand 'are interconnected` byf-aV U-shaped-.d-uct. Thus, the airandpressure produced i by l the fone fan f unit are: transferred i to. theinlet oftheother fan unit for steppingup such pressure.

VDetailed construction As shown particularly in Figures land 3, thetwo-stage blower assembly is comprised of two single width, singleinlet,blower housings 11 and 12 and two adjacent inlet'boxes 13 and 14, whichare disposed between, and are associated respectively with, saidVhousings 1l and l2, said'housings and inlct-boxes-being fabricatedprimarily from sheet-form materials, as 'shown in Figure 3.V The mutualside walls 16.and 17 between the corresponding blower housings andinlet-boxes are provided with coaxial' inlet' cones i8 and'l9. Theblower housings and inlet-boxes are all connectedtogether. and saidinlet boxes havev a-common intermediate-wall 2l. A shaft 22 extendscompletely through both inlet boxes and both blower housingscoaxially.with the inlet cones 1 randy 19. An appropriate shaft seal 20l (Figure3). may be provided inl the wall. 23 around theshaft 22 for sealingpurposes.' Said shaft is rotatably supported nearits opposite'ends bymeans of the bearings -23 and 24,- which maybe sub-v stantiallyconventional in construction and which are blower housing il, inletbox'. 21.3 and wheel Sal-comprise a iirst blower unit 34 in theblowerassemblyl0, whereas the-blower housing l2, inlet box 14 and wheel32 comprise a second blower unit- 35 .in said blower. assembly l0.

The common wall 2l between the inlet boxes 13 and 14 is, in thisparticular embodiment; sloped with respect' to the axis of the shaft22,. and the inlet openings 37 and 38 in the inlet boxes 13 and 14,.respectively, enter opposite sides, such as,.for. example, the bottom`and the top, of the assembly 19, where said common wall 2] is at themaximum divcrgency with respect to the particular inlet box. Thisarrangement materially reduces the spacerequired by said inlet boxesbetween the blower housings and thereby permits the use of a. smallershaft 22-than would otherwise be permissible.

In this particular embodiment, the inlet opening 37 `is in the bottom ofthe inlet box 13 and the inlet opening'38 is in the top of the inlet box14, and bothblower housings l1. and 12 have upwardly,dischargingoutlets40 and 4i, respectively. The discharge directions ofthe two blowerhousings ll and l2 may vary with respect to each other. However, becausethe two wheels 3i. and 32 are always rotating in the same direction, therotational directions of their discharge will always be the same, thatis, they will both have either a clockwise or a counterclockwisedirection of discharge. The direction of discharge from the outlet 4) ofthe rst blower unit 34 will be substantially the same, hence on the sameside of the assembly 10, as the direction of entry of the inlet opening38 of the inlet box 14 associated with the second blower unit 35. Thus,the outlet 40 can be easily connected to the inlet opening 38 by meansof a U-shaped connector duct 42. In this particular embodiment, saidduct 42 has an expanding cross-section because the area of said outlet40 is smaller than the area of said inlet 38. However, the area of saidoutlet 40 may be the same as, or larger than, the area of said inlet 38.

Operationv The operation of the two-stage blower assembly 10 commenceswith air being drawn through the inlet opening 37 (Figure 3) in theinlet box i3 and thence passing through the inlet conel'where it entersthe inlet of the blower wheel 31 and is driven thereby through theoutlet 40 in the blower housing 11. The air leaving the outlet 40 isconveyed to the inlet opening38 by the expanding connector. duct'42which, inthis embodiment, reduces the air'velocity, thereby increasingthe eciency of the rstbloWer'unit' 34. Such air, having thus reached theinlet' box 14 of the ,second blower unit r35', is drawn thereby'throughthe* inlet cone 19'where the blower wheel 32 discharges suchair'through'the outlet opening 41 into any convenient, conventional,duct'system, not shown. It; has been found'th'at', by use of' thetwo-stage blower assemblylt'substantially as disclosed, air departingfrom the outlet-'40 in' the rst stageblower unit 34 at a givenpressure-andvolume'will depart 'from' the-outlet 4l in the secondstage-blower uniti35 'with its pressure approximately doubled.` It hasalso 'been found that, by having the V'outlet 40 and -inlet opening 38face in substantially the-same direction; the air moving through theconnector duet'42 enters the inlet cone 19 without rotational componentsabout the shaft 22, which components canmateriallyreduce-the'performance of the second blower unit 35. Thisis'due tothe fact 'that the Velocity component offthe air flow from theoutlet 4i) to the inlet cone i9 is in ai direction substantiallyparallel with al plane including the axis of said `shaft`1and parallelwith the direction of discharge from: said outlet 405v The fact that.the-wheels 31-and 32 are-disposed very close tothe bearings 23 and 24,respectively, makes it possible touseashaft 22 which is considerablysmaller int maximum diameter and, therefore, in weight than the shaftwouldhave to be if the blower wheels were mounted,accordingftoxpresent'teachings, at or near the center thereof.Accordingly, the bearings 23 and 24, as well as theirsupport pedestals216'y and 27, may also be substantially smaller than would otherwise berequired if said wheels weremounted at the center of the shaft.Because'the'blower wheels 31 and 32am-mounted adjacent to the ends ofthe shaft, where the shaft has its smallest diameter; th'efwheelahubs 33may also be of a minimum size and Weight.' This not only-permits the useof a shaft 22y havingV a' minimum'. size andi weight, but also resultsin aof-'interference'with the airflow through thefanwh'eels:andythereforethe b'est performance available.

In order to meet' specific installation requirements, the outlet 40 ofthe first blower unit 34 may face in a difierent direction, such' assidewardly, lthan the outlet opening 41'in the second.' blower unit 35iHowever, the outlet 40 and inlet: opening willl normally face insubstantially the-samedirectionto'eliminate undesirable rotationalcomponents in the air flow.' Further, where other factors, such Yas easeof fabrication,'. are more important than the maximum saving in:.cost=and 'space requirements, the commonwall 21 may'be substantiallyperpendicular to the axis ofi-the shaft422, Athereby requiring anincrease in the space occupied/by the. inlet 'boxes 13 and 14. Such acondition may occur where it is'desirable to have the inlet opening 37*atanV angleof 90, instead of 180 as shown, tothe inlet opening-38.However, the most desirable arrangement: includes a sloping common wall21.

Figure 4- illustrates a multiple blower assembly 50, comprised'ofcentrifugal blowers S1, 52 and 53 and inlet boxes 55, 56 and 57. Theblowers 51 and 52 and the inlet boxes 55 and 56 may be arranged insubstantially the same manner as that set forth hereinabove with respectto the assembly of Figure 1. However, the outlet of blower 52 isconnected by the duct 58 to the inlet box 57 associated with the blower53, thereby producing the three-stage blower assembly 50. The blowerwheels (not shown) within the blowers 51, 52 and 53 may be supportedupon a single shaft 59, which is supported upon the bearings 61 and 62.

Although particular, preferred embodiments of the invention have beendisclosed hereinabove for illustrative purpose, it will be understoodthat variations or modifications of such disclosure, which lie withinthe scope of the appended claims, are fully contemplated.

I claim:

l. A multi-stage, centrifugal blower assembly for moving a gas,comprising: first and second, single inlet and single outlet,centrifugal blower housings spaced from each other and having axiallyaligned inlet openings on the opposing sides thereof; a pair of inletcones secured respectively to said housings concentric with and adjacentto said inlet openings therein; rst and second adjacent inlet boxesdisposed between, and communicating respectively with, the inletopenings in said housings, said inlet boxes having single inlet openingsfacing in substantially opposite directions, the inlet opening of thesecond inlet box facing in substantially the same direction as theoutlet opening of the first blower housing, said housings and inletboxes being fabricated primarily from relatively thin materials, wherebythe combined length of said housings and inlet boxes, axially of saidinlet cones, is held -to a minimum; a shaft extending through saidblower housings and said inlet boxes coaxially with said cones; bearingmeans adjacent to the remote, outer sides of said housings and rotatablysupporting said shaft, said bearings providing the sole support of saidshaft therebetween; a pair of centrifugal blower wheels supportedentirely upon said shaft and rotatable therewith within said blowerhousings, each wheel being disposed between and adjacent to, but spacedfrom, one of said bearing means and the adjacent one of said cones; anda substantially U-shaped connecting duct extending between the outletopening of said rst blower housing and the inlet opening of said secondinlet box.

2. 'Ihe structure of claim 1 wherein said inlet boxes have a common,intermediate and relatively thin, substantially planar wall whichdiverges with respect to the opposing wall of each box toward the inletopening in each box, said common wall having a central opening throughwhich said shaft is freely received; wherein the axis of curvature ofsaid connecting duct is substantially perpendicular to the axis of saidshaft, whereby air enters said second blower housing substantiallywithout rotational components about said axis of said shaft; and whereinsaid U-shaped connector duct has a greater cross-sectional area at itsoutlet end, adjacent to the inlet opening of said second inlet box, thanit does at its inlet end, adjacent to the outlet opening of said rstblower housing.

3. A two-stage, centrifugal blower assembly for moving air, comprising:first and second single inlet and single outlet, centrifugal lblowerhousings spaced from each other and having coaxial inlet openings on theopposing sides thereof; a pair of inlet cones secured respectively tosaid housings adjacent to and concentric with the inlet openingsthereof, said cones extending into said housings; rst and secondadjacent inlet boxes disposed between, and communicating respectivelywith, the inlet openings in said housings, each inlet box having asingle inlet opening disposed in the periphery thereof, the inletopenings of said boxes facing in substantially opposite directions andthe inlet opening of said second box facing in substantially the samedirection as the outlet opening of the rst blower housing, the walls ofsaid housings and inlet boxes being fabricated primarily from sheet-formmaterials, whereby the combined length of said housings and inlet boxes,axially of said inlet cones, is held to a minimum, said inlet conesextending into said inlet boxes and said housings; a shaft extendingthrough said blower housings and said inlet boxes coaxially with saidcones; bearing means adjacent to the remote, outer sides of saidhousings rotatably supporting said shaft near the ends thereof, saidbearings being located at a minimum distance from each other andproviding the sole support for said shaft; a pair of centrifugal blowerimpellers secured to and supported entirely by said shaft for rotationrespectively within said blower housings, said impellers being adjacentrespectively to said bearing means, and each impeller having an inletrim concentric with, adjacent to and spaced from one of said cones; anda substantially U-shaped connecting duct extending between the inletopening of said second box and the outlet opening of said rst blowerhousing.

4. A multi-stage, centrifugal fan assembly for moving a gas, comprising:first and second, single inlet and single outlet, centrifugal fanhousings spaced from each other and having axially aligned inletopenings on the opposing sides thereof; a pair of annular structuressecured respectively to said housings concentric with and adjacent tosaid inlet openings therein; first and second adjacent inlet boxesdisposed between, and communicating respectively with, the inletopenings in said housings, said inlet boxes having single inlet openingsfacing substantially radially from the axis of the inlet openings ofsaid housings in directions displaced circumferentially from each otherat an angle in excess of degrees around said axis of the inlet openingsof said housings, the inlet opening of the second inlet box facing insubstantially the same direction as the outlet opening of the lirst fanhousing, said housings and inlet boxes being fabricated primarily fromrelatively thin materials, whereby the combined length of said housingsand inlet boxes, axially of said annular structures, is held to aminimum; a shaft extending through said fan housings and said inletboxes coaxially with said annular structures; bearing means adjacent ltothe remote, outer sides of said housings and rotatably supporting saidshaft, said bearings providing the sole support of said shafttherebetween; a pair of centrifugal fan wheels supported entirely uponsaid shaft and rotatable therewith within said fan housings, each wheelbeing disposed between and adjacent to, but spaced from, one of saidbearing means and the adjacent one of said annular structures; and asubstantially U-shaped connecting duct extending between the outletopening of said first fan housing and the inlet opening of said secondinlet box.

References Cited in the le of this patent UNITED STATES PATENTS1,408,291 Haentjens Feb. 28, 1922 1,536,573 Drysdale et al May 5, 19252,331,299 Blom Oct. 12, 1943 2,368,962 Blom Feb. 6, 1945 2,407,987Landberg Sept. 24, 1946 FOREIGN PATENTS 316,807 Great Britain Aug. 8,1929 376,149 Germany May 24, 1923

